With the first weekend drawing to a close, Mr Xenophon and his party have already come under sustained attack from both the Liberal and Labor camps.

Labor suggested Premier Jay Weatherill's political opponents were "born with silver spoons in their mouths" while Liberal leader Steven Marshall said SA-BEST would bog down the next government with endless inquiries.

Hitting back, Mr Xenophon said he had "always found wooden spoons to be much more practical".

He also described Mr Marshall's move to announce a plan for the first 100 days of a Liberal government as "the height of arrogance" coming so early in the run-up to the March 17 poll.

"Mr Marshall is already thinking about how he arranges the furniture in the premier's office," he said.

But Mr Xenophon wasn't surprised at being so quickly and forcefully targeted.

"I always knew it would be hard and vicious, but this is what happens when you take on the duopoly," he said.

"This is the biggest challenge to the Liberal and Labor duopoly that they've ever seen in this state and indeed, probably around the country.

"They're not going to give up their duopoly lightly. It's a cosy little club."

Australian Associated Press